This invention relates to a blast furnace installation, more particularly a blast furnace installation which is constructed to efficiently mount and dismount an inclined chute device and to decrease the load upon the furnace to substantially zero.
It is a recent trend to increase the capacity of a blast furnace, and at present ordinary blast furnace has an inner volume of 4000 m.sup.3, a furnace bottom diameter of about 15 m, and a yield of cast iron of 8000 tons per day. As a consequence, apparatus for charging a large quantity of raw materials into a blast furnace of such a large capacity has a large size and weight. In U.S. Pat. Nos. 3,966,062 and 4,050,679 assigned to the same assignee as this invention is disclosed a blast furnace installation comprising a blast furnace, and a raw material charging apparatus, wherein the raw material charging apparatus comprises a rotary hopper mounted above the furnace top, a conveyor for feeding raw materials to the rotary hopper, a disc shaped hollow impeller located beneath the rotary hopper, a stationary inclined chute device surrounding the impeller, and an electric motor disposed above the rotary hopper to drive the impeller at a high speed. The total weight of the blast furnace installation excepting the inclined chute is supported by supporting posts apart from the furnace and the inclined chute is supported merely by the iron plate on the furnace top so that the chute not only applies an excessive stress to the furnace but also causes deformation and warping of the furnace due to thermal expansion. Thus, this design was found unsuitable for practical use.
The inclined chute concentrically surrounds the impeller for charging the raw materials and is provided with three separate twisted passages extending downwardly from the inlet of the raw materials to three outputs located at points adequate to charge the raw material. To make easy mounting and dismounting at the time of repair and exchange the lower end of the inclined chute is constituted by a flange and a supporting ring and hermetically mounted on the top surface of the furnace. With the construction disclosed in U.S. Pat. No. 3,966,062 the total weight of the inclined chute is applied to the top of the blast furnace.
When the inclined chute becomes faulty and it is necessary to quickly repair or exchange it, the problem becomes more serious. More particularly, with the raw material charging apparatus, when it is necessary to entirely exchange it or a portion thereof particularly the inclined chute it is necessary to sequentially dismount all upper structures, i.e., the impeller, the rotary hopper, and the driving motor of the impeller so that it requires much time and labor thus reducing the yield of the furnace.